Merge main into next: resolve conflicts, rewrite Dockerfile for Go 1.23

- Resolve merge conflicts (README.md, TODO.md, go.mod) keeping next's versions
- Rewrite Dockerfile: replace sneak/builder:2022-12-08 (Go 1.19) with
  golang@sha256-pinned (Go 1.23), add golangci-lint for future use
- Remove references to deleted vendor.tzst, modcache.tzst
- Simplify to standard multi-stage build: check + build + scratch final image
- Keep module path sneak.berlin/go/mfer from next branch
- Add Makefile targets: check, fmt-check, hooks (per REPO_POLICIES)
- Pin golangci-lint@v2.0.2 in devprereqs
- Dockerfile version/date comment on pinned image hash
- make check runs test + fmt-check (lint deferred to follow-up issue)

Dockerfile

@@ -1,37 +1,18 @@
-################################################################################
-#2345678911234567892123456789312345678941234567895123456789612345678971234567898
-################################################################################
-FROM sneak/builder:2022-12-08 AS builder
-ENV DEBIAN_FRONTEND noninteractive
-WORKDIR /build
-COPY ./Makefile ./.golangci.yml ./go.mod ./go.sum /build/
-COPY ./vendor.tzst /build/vendor.tzst
-COPY ./modcache.tzst /build/modcache.tzst
-COPY ./internal ./internal
-COPY ./bin/gitrev.sh ./bin/gitrev.sh
-COPY ./mfer ./mfer
-COPY ./cmd ./cmd
-ARG GITREV unknown
-ARG DRONE_COMMIT_SHA unknown
+# golangci/golangci-lint:v2.0.2 (2026-03-14)
+FROM golangci/golangci-lint@sha256:d55581f7797e7a0877a7c3aaa399b01bdc57d2874d6412601a046cc4062cb62e AS lint-bin
+
+# golang:1.23 (2026-03-14)
+FROM golang@sha256:60deed95d3888cc5e4d9ff8a10c54e5edc008c6ae3fba6187be6fb592e19e8c0 AS builder
+COPY --from=lint-bin /usr/bin/golangci-lint /usr/local/bin/golangci-lint
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+# Touch .pb.go so make does not try to regenerate via protoc (file is committed)
+RUN touch mfer/mf.pb.go
+RUN make check
+RUN cd cmd/mfer && go build -tags urfave_cli_no_docs -o /mfer .
 
-RUN mkdir -p "$(go env GOMODCACHE)" && cd "$(go env GOMODCACHE)" && \
-    zstdmt -d --stdout /build/modcache.tzst | tar xf - && \
-    rm /build/modcache.tzst && cd /build
-RUN \
-    cd mfer && go generate . && cd .. && \
-    GOPACKAGESDEBUG=true golangci-lint run ./... && \
-    mkdir vendor && cd vendor && \
-    zstdmt -d --stdout /build/vendor.tzst | tar xf - && rm /build/vendor.tzst && \
-    cd .. && \
-    make mfer.cmd
-RUN rm -rf /build/vendor && go mod vendor && tar -c . | zstdmt -19 > /src.tzst
-################################################################################
-#2345678911234567892123456789312345678941234567895123456789612345678971234567898
-################################################################################
-## final image
-################################################################################
 FROM scratch
-# we put all the source into the final image for posterity, it's small
-COPY --from=builder /src.tzst /src.tzst
-COPY --from=builder /build/mfer.cmd /mfer
+COPY --from=builder /mfer /mfer
 ENTRYPOINT ["/mfer"]